The 2008 financial crisis made a regime change for interest rate swaps. Before the crisis, interest rates were relatively consistent and that is what allowed financial industry to structure a single curve to valuate and price interest rate swaps. In the middle of 2007 however, a few anomalies happened that could be detected on interest rate markets which unwillingly forced participants on market to rethink their valuation and pricing framework. Liquidity and credit problems became extremely important in the valuation and pricing of interest rate swaps, so the new market structure led to the acceptance of a new framework, so called multi-curve framework. A single yield curve wasn't adequate any longer to get discount factors and forward rates because now, there was a demand for numerous separated curves to get narrative for the various dynamics of derivative instruments of diverse maturities. In essence, this thesis interprets the way the valuation and pricing of interest rate swaps has expanded and evolved from a classic framework to a modern framework. It also analyses and the two mentioned pricing approaches by comparison and by examination of two points in time. Therefore, the multiple-curve approach should be nowdays used in case of valuation and pricing of interest rate swap.